Apparatus for removing cured concrete articles from pallets

ABSTRACT

Apparatus and method for removing cured concrete articles, particularly prestressed concrete articles, from pallets in which they are cast and cured which includes feeding and guiding pallets containing cured articles into predetermined position, cutting by saws the stressing cables to free castings from the pallets, inverting the pallets beneath plungers which enter openings in the pallet bases and press castings from the pallets onto receiving means which lower them to an accumulating area, reverting the pallets to their previous orientation, driving the cut cable ends from the pallet retaining means by swinging hammers, and cleaning, oiling and restranding the empty pallets, the pallets being moved step-by-step from one operating procedure station to the next from entering into the apparatus to exit therefrom.

P. Cone Filed: July 28, 1970 Appl. No.: 58,759

Division of Ser. No, 872,662, Oct. 30, 1969, Pat. No. 3,611,518, which is a division of Ser. No. 660,133, Aug. 1 1, 1967, abandoned.

[52] U.S. Cl. ..425/289, 425/350, 425/439, 425/444 [51] Int. Cl ..B28b 13/04, B28b 23/06 [58] Field of Search ..425/350, 351, 439, 425/444, 111, 88, 289; 249/67, 68; 25/2, 118 T, 410, 120

[56] References Cited UNITED STATES PATENTS 3,305,907 2/1967 Baker ..25/118 T X 2,402,368 6/1946 Cantrall et a1. ..25/4l L United States Patent [111 3,732,053

Glass I May 8, 1973 54] APPARATUS FOR REMOVING CURED 3,076,238 2/1963 Rekartm ..169/344 x CONCRETE ARTICLES FROM 2,319,778 5 1943 Fisk ..25/120 UX 3,233,027 2/1966 Wennstrom.. ..,..25/l18 T X PALLETS 2,713,710 7/1955 Holland ..25/l20 X [75] inventor: Ercell L. Glass, Tampa, Fla. 3,577,610 5/1971 Margolin ,.25/2

[73] Assignees: J. L. Cone, Jr.; C. W. Cone; Douglas Primary Examiner-J. Spencer Overholser Assistant ExaminerB. D. Tobor Attorney-Stevens, Davis, Miller & Mosher [57] ABSTRACT Apparatus and method for removing cured concrete articles, particularly prestressed concrete articles, from pallets in which they are cast and cured which includes feeding and guiding pallets containing cured articles into predetermined position, cutting by saws the stressing cables to free castings-from the pallets, inverting the pallets beneath plungers which enter openings in the pallet bases and press castings from the pallets onto receiving means which lower them to an accumulating area, reverting the pallets to their previous orientation, driving the cut cable ends from the pallet retaining means by swinging hammers, and cleaning, oiling and restranding the empty pallets, the pallets being moved step-by-step from one operating procedure station to the next from entering into the apparatus to exit therefrom.

13 Claims, 20 Drawing Figures PATENTED 81975 3,732,053

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SHEET PATENTED W 75 PATENTED W 73 sum 11 0F 1 C ox INVENTOR EmcmL Lmvm m%s PATENTEDHAY 81975 SHEET 13 [1F 15 Eacem Lmw Gms$ PATENTED MAY 8 975 sum 1w or 1 APPARATUS FOR REMOVING CURED CONCRETE ARTICLES FROM PALLETS The present application constitutes a division of my application Ser. No. 872,662 filed Oct. 30, 1969, now U.S. Pat. No. 3,61 1,5 18, which application is a division of 'my application Ser. No. 660,133 filed Aug. 1 l, 1967, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a method and apparatus for removing cured concrete articles from pallets, or molds, in which they have been cast and cured, particularly adapted for the removal of prestressed concrete articles from pallets in which stressing cables are held under tension during casting and curing of the concrete.

In casting prestressed concrete articles, stressing cables in desired pattern arrangement are strung between headers of a mold and attenuated to the extent required to place them under predetermined tension. While the cables are held tensioned, the concrete is poured, compressed and cured. The cables are then cut to free the article from the mold, and the article is lifted from the mold.

Two Pat. Nos. 3,128,521 and 3,305,907, both in the name of Robert S. Baker, are directed to apparatus for automatically placing cables in portable pallets, stressing the cables and holding the cable tension by the pallet, pouring the concrete into a mold formed by the pallet and a mold member, stripping the mold member from the molded article and removing the molded article on the pallet for curing. Pat. No. 3,305,907 goes further and, in addition to the above, discloses apparatus for cutting the cables from the pa]- let to release the tension to the concrete article to stress it, and apparatus for removing the article from the pallet after the cables are cut.

The article removing means disclosed in Pat. No. 3,305,907 consists of means to engage, and hold, the pallet while the cured article is gripped by a vacuum head and lifted from the pallet. The compression of the concrete into the pallet during molding conforms the article, when cured, so closely to the pallet recess that considerable force is required to separate the two. If the vacuum head pulls free from the article, the entire conveying line must be stopped until the article is removed from the pallet. In addition, the article, when lifted free, must be conveyed by some traveling overhead mechanism to a place of deposit. As the vacuum separating head must hold the article during transport, the movement of pallets to and from the removing station must be timed to separating and conveying actions of the vacuum head.

SUMMARY OF THE INVENTION The general object of the present invention is to provide improved means for freeing and separating cast concrete articles from pallets in which they are formed and cured.

A more specific object is to provide mechanical means for inverting pallets with cured cast articles in them, and forcefully pressing the articles from the pa]- lets.

A further object is to provide a receiver which is removable to a position underlying a casting to be removed, to receive it and lower it onto a discharge conveyor.

Still another object is the provision of cast article removing mechanism,as set out above, which is part of a conveying system for transporting cured articlesin pallets to a cable cutting station, the casting removal station and a cut cable end and anchor chuck jaw removing station, and for transporting the empty pallet along an area where it is prepared for another casting operation.

Yet a further object of the invention is to provide a novel mechanism for removing the cut cable ends and anchor jaws from pallets, after the castings have been taken out.

It is also an object to provide a new method for handling pallets with cured concrete articles in them, to remove the articles, to remove cut cable ends and anchor jaws and to prepare the pallets for a new casting operation.

Other objects of the invention will become apparent from the following description of one practical embodiment thereof, when taken in conjunction with the drawings which accompany, and form part of, this specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of apparatus embodying the principles of the present invention, depicting a conveyor path along which a plurality of operating stations are arranged in spaced relation;

FIGS. 2A, 2B, 2C and 2D, together, illustrate the apparatus in top plan on a greatly enlarged scale;

FIGS. 3A, 3B, 3C and 3D, together, show a side elevation of the apparatus shown in FIG. 1;

FIG. 4 is a transverse, vertical section through the machine, taken substantially on the line 44 of FIG. 3B, illustrating the mechanism at the saw station of the apparatus;

FIG. 5 is a fragmentary longitudinal section, taken on the line 5-5 of FIG. 4, and shown on an enlarged scale;

FIG. 6 is a vertical, transverse section, taken on the line 6-6 of FIG. 3B, illustrating the apparatus at the casting removal station;

FIG. 7 is a fragmentary longitudinal section, taken on the line 7--7 of FIGJ6 and being shown on an enlarged scale with the parts in position to receive a pallet;

FIG. 8 is a perspective view of one of the pallet header receiving, and inverting, members employed at the casting removal station;

FIG. 9 is a view similar to FIG. 7, but with a pallet at the station in inverted position and the' elements in position to remove the casting from the pallet;

FIG. 10 is a fragmentary section taken on the line l0- --l0 of FIG. 9;

FIG. 1 I is a fragmentary perspective view illustrating the manner of removing a casting from a pallet;

FIG. I2 is a fragmentary, vertical, transverse section, taken on the line 12-42 of FIG. 3C, illustrating mechanism at the station for removing the cut cable ends and anchor chuck jaws, the parts being shown on an enlarged scale;

FIG. 13 is a fragmentary longitudinal section, taken DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention is concerned with the handling of pallets upon which concrete is poured and molded, and the molded member supported until cured. The pallets can take any shape, depending upon the contour of the article to be cast, but, for convenience, a pallet has been illustrated and will be described for use in making prestressed railway ties.

Referring to FIGS. 11, 12 and 13, it will be seen that the pallet 1 is composed of a body 2 with headers 3 at each end. The body is formed as an upwardly opening channel, having box-type sides 4 and a bottom 5. The inner walls of the box sides and the bottom are made in desired contour to produce a casting of predetermined shape. Headers 3 are in the form of outwardly opening channels, having top and bottom flanges 6 and 7 and an interconnecting back wall 8. The back wall has a plu rality of openings 9, in desired pattern, to receive the ends of cables used for stressing the concrete members. Anchors 10, of the usual type having a plurality of movable chuck jaws, are fixed to the outer sides of the back walls 8 of the headers in alignment with the openings 9, so as to receive and grip the ends of cables which project through the openings 9. The bottom of the body of the pallet will have several openings 11, through which the surface of the cast article will be visible, and through which the surface of the cast article can be contacted. There is also a raised guide 12 on the bottom of the pallet to provide means for positively locating the pallet transversely of the apparatus which will be described.

The present invention proposes to remove cured ties from pallets, such as pallets l, and prepare the pallets to receive another casting by first cutting the stressing cables between the tie ends and the pallet headers (See FIG. 4) to impose the cable tension upon the tie and to free the tie from attachment to the pallet. This is done by cutting first the two top strands (See FIG. 5) then cutting the two bottom strands. The strands are cut first at one side of the tie, then the other. The cut ends of cable remain locked in the anchors 10. The pallet, with the tie in place, is next inverted, and held against downward movement, while pressure is exerted against the surface of the tie through the punch-out openings 11 to forcibly eject the tie from the pallet. As the tie falls free of the pallet, it is caught and gently lowered onto a repository. The pallet is then reverted to its original position, and the cut ends of cable and the chuck jaws which hold them are driven from the anchor housing by delivering a blow against the cut cable ends. The steps of cleaning, oiling, restranding and tensioning the strands are then followed to prepare the pallet for a new casting.

FIG. 1 of the drawings shows a general top plan view of apparatus for carrying out the above method. It consists of a frame 13, which defines an elongated pallet path 14 having an entrance end 15 and an exit end 16, and along which are positioned a plurality of operating stations. These include a pallet advancing and positioning station 17, a cable cutting station 18, a pallet inverting and tie removing station 19, a cable end removing station 20, and a pallet preparing station 21. Means, to be described, which will be under selective control of an operator, are provided for advancing pallets along the path to, and through, the various stations where the several operations are performed. The apparatus also includes a tie receiving and lowering mechanism 22, located beneath the station 19, and a separated tie accumulating station 23 below the pallet path, extending substantially the full length of the stations 17, 18 and 19.

The pallet path 14 is defined by a pair of transversely spaced box-like rails 24 having wear plates 25 extending along their tops. The rails are so spaced that the wear plates underlie the headers of pallets placed upon them (See FIG. 4). The rails are continuous throughout the machine, except for a short area at the inverting and tie removing station 19, where they are replaced by a portion of that mechanism, as will be described. The rails are supported upon legs 26, forming part of the frame 13, and the legs are interconnected by suitable transverse beams 27. These elements, together with the special framing at the several stations, which will be described, complete the main frame 13.

The pallets are placed upon the rails 24 at the entrance end 15 of the pallet path, and they are advanced along the length of the apparatus by means of an advancing chain 28 which moves the pallets through the advancing and positioning station 17, an advancing rack 29 which moves the pallets through the cable cutting station 18 and to the inverting and tie removing station 19, and an advancing rack 30 which moves the pallets from the tie removing station 19 and through the cable end removing station 20 and pallet preparing station 21.

The chain advance 28 consists of two separate chains 31, one adjacent each of the rails 24 throughout the advancing and positioning station 17. The chains ride in channel guides 32 which are mounted upon transverse beams 27 between the legs 26 of the station 17. At the forward end of the apparatus, chains 31 pass around sprockets 33 on shafts 34, mounted in suitable bearings on a plate 35 which extends forwardly from the ends of the guides 32. Suitable chain tightening means 36 may be mounted on the plate also. The rear ends of the chains pass around sprockets 37 carried by a drive shaft 38, mounted in plates 39 projecting rearwardly from the guides 32. Shaft 38 can be driven in any desired manner, such as by chain 40 which passes around sprockets on a motor unit 41 and the drive shaft 38. Each chain carries a dog 42 which projects upwardly from the top flight a sufficient distance to engage pallets seated on the rails 24. Although not shown in detail, the dogs will be freely depressible so as to move downwardly and under pallets when the chain is retracted, yet spring to upright, pallet-engaging position when free from a pallet.

One or more pallets bearing cured ties may be placed upon the rails 24 by means of a fork lift, or other suitable machine, and when the motor 41 is started, by means of electric circuits to be described, the dogs 42, being in alignment, will engage the rearmost pallet of the group and move the pallets along the rails. If the pallets are canted in their positions, the pressure of the dog first contacting the pallets will force the pallets into proper alignment normal to the extent of the rails. As the pallets move along the rails, their downwardly projecting guides 12 will enter between the spaced, con- When the guide 12 is within the parallel section of the guide, the pallets will be precisely positioned transversely of the pallet path. The sword has its converging blades 43 mounted upon a cross-brace 45 between the guides 32, and its parallel section supported at the cable cutting station 18.

By operating the chains 31 to move pallets into the apparatus to the end of the chain travel, and then reversing the chains to bring the dogs 42 back to the entrance end 15, more pallets can be brought in and accumulated on the rails to await carriage into the cable cutting station. Pallets accumulated on the rails are picked up and moved singly into the cable cutting station by the advancing rack 29. I

Rack 29 consists of two bars 46, mounted for longitudinal reciprocating movement adjacent the rails 24. The bars have V-shaped guides 47 extending the lengths of their sides that ride in rollers 48 and 49, secured to the rails 24 and angle members 50, respectively, the angle members 50 forming part of the frame (see FIGS. 23, 3B, 4 and 5). Each rack carries a plurality of spring biased dogs 51, similar to the dogs 42, which are equally spaced along the bars a distance greater than the width of a pallet, so that they may posiate bars 46 and to advance pallets is controlled manually, as will be described Rack 29 will move pallets to and through the cable cutting station and into the inverting and tie removal station. Rack 30 will pick up empty ties from the inverting and tie removal station and advance them step-bystep along the remainder of the pallet path.

Rack 30 is very similar to rack 29, having bars 56 with V-guides 57 mounted for sliding movement in rollers 58 and 59 supported, respectively, on rails 24 and angle members 50. The bars carry dogs 60, which are spaced apart a much greater distance than the dogs 51 to provide greater spacing between the empty pallets for the manual pallet-preparing operations. Cylinders 61, mounted on frame legs 26 at the pallet preparing station 21, have their piston rods 62 connected to brackets 63 on the bars 56. Rack 30 differs from rack 29 in that bars 59 have extensions 64 at their ends adjacent the inverting and tie removal station that carry an end dog 65. Extensions 64 are of smaller cross-section than bars 56, and are unsupported by rollers. The extensions and dogs 65 are to enter the inverting and tie removing station to withdraw empty pallets after the ties have been removed.

Pallets on the path are brought first to the cable cutting station 18. The structure of that station appears in FIGS. 1, 2B, 3B, 4 and 5, and FIGS. 4 and 5 show the detailson a larger scale.

Station 18 has an auxiliary frame 66 extending transversely across the main frame, consisting of pairs of spaced legs 67 rising on either side of the main frame and interconnected at their tops by a top beam 68. Top, intermediate and bottom plates 69, 70 and 71, respectively, span the respective pairs of legs and form mounting platforms at each side of the frame for the operating mechanism of the station.

Spaced, parallel sliderods 72 are supported at their ends in brackets 73 secured to the plates 69 and 70,

with one pair of rods being at each side of frame 66.

Each pair of rods slidably mounts a carriage 74, the carriage being composed of a base platform 75 having supports 76 projecting from its bottom and slidably mounted on rods 72 to permit the carriage to move along the rods. The carriage is moved by means of a cylinder 77 that is connected to plate 71 and has its piston rod 78 attached to the carriage.

Each carriage 74 carries a motor 79 having a cable cutting saw 80 fixed to its shaft 81. The motors, shafts and saws of the two carriages will be oppositely mounted so that the saws will be positioned inwardly of the carriages to overlie pallets on the pallet path at the station. The saws .will be positioned to enter the pallets adjacent the headers, in the spaces between the headers and the ends of the concrete members. In the embodiment shown, the tie ends are inclined and the slide rods 72 are at an angle to the vertical to improve the entry positions of the saws. This arrangement would not necessarily be present in apparatus designed to remove concrete articles of different shape.

The saws are shielded by' guards 82 mounted upon the shafts 81. The guard is substantially semi-circular, covering the upper half of the saw, but its backwall 83 extends downwardly at the sides to form pallet embracing arms 84. The arms have their facing edges parallel at the top, as at 85, and tapered at thebottom, as at 86, so that when asaw is lowered, a pallet which may be slightly misaligned will be engaged by oneor the other of the tapered edges 86 and be cammed back into proper alignment to pass within the parallel area between the upper portions of the arms .84 and be held against movement during the cutting operation. This will insure proper registration of the pallets with the saws and stability of the pallet during cutting.

The cables will be cut in altemation'first one side then the other, as will be described, and the pallet moved by advancing rack 29 to the pallet inverting and tie removing station 19. FIGS. 1, 2B, 3B and 6 through 1 1 illustrate this station.

Pallet rails 24 and the main frame 13 are discontinubus at the station 19, but have their ends adjacent the station connected to opposite side of a special frame 87 at this station. This frame is erected upon a flat base 88 on which there is a pair of parallel l-beams 89, extending transversely of the apparatus. At each side, stanchions 90 rise vertically from the sides of beams 89. The stanchions on either side are bridged by plates 91, which form bases for the frame superstructure. On one side, an additional plate 92 provides a platform for a pallet inverting motor 93. The frame superstructure comprises pairs of uprights 94, resting upon each plate 91, bridged at their tops by beams 95. A transverse beam 96 extends completely across the apparatus, with its ends seated upon beams 95. V

The platforms 91 carry bearings 97 in which shafts 98 are mounted. These shafts form part of rotating heads 99, which receive, and control, pallets at the station. One of the shafts is coupled to motor 93 by means of a clutch 100. Each rotating head is in the form of a vertically positioned disk 101, concentric to the shaft 98 on which it is mounted, and having a grooved block 102 on its inner face that seats spaced pallet rails 103. The rails are parallel to one another and equidistant on opposite sides of the projected axis of shaft 98. The rails are spaced apart such distance as to permit the headers of pallets to ride over them, with the header flanges 6 and 7 passing on opposite sides of the rails so as to confine the rails within the headers. A bearing plate 104 projects from each disk above the top rail 102, when the disks are in pallet-receiving position, to support the pallets when inverted and to take the pressure exerted upon the pallet during tie removal. The plate 104 may be suitably braced by gussets 105.

When a pallet is moved off of the end of the rails 24 into the inverting and tie removing station 19, the pallet headers will move in surrounding relation to the pallet rails 103. When the pallet is wholly within the station, it will lie wholly within a cylinder defined by the projected peripheries of the disks 101. If the motor 93 is started, the rotary head 99 connected to it will rotate and this rotation will be transmitted through the pallet to the rotary head 99 at the opposite end of the station. One-half revolution of the rotary heads will invert the pallets. In order to prevent the pallets from slipping out of the rotary heads during the inverting movement, arcuate wear plates 106 are mounted just below the projected cylinder of the rotating heads to provide a bearing surface for the pallet ends to retain their position. The arcuate wear plates are mounted upon beams 107 connected to the stanchions 90.

When the pallets have been inverted, their bottoms will be uppermost and the punch-out openings 11 will be on top. In order to remove the ties, punch-out cylinders 108 are pivotally connected, as at 109, to brackets 110 mounted on the underside of the transverse beam 96. The cylinder rods 111 have heads 112 of a size to pass freely through the openings 11 in the pallet to contact, and press out, the cast article. In order for the punch-out stroke of cylinder 108 to be a short one, the bottom of the cylinder is quite close to the pallet when the cylinder occupies a vertical position as shown in FIG. 9. This, however, requires that the pistons be moved from the vertical position during periods of rotation of the pallet. To this end, the cylinders 108 are connected to piston rods 113 of positioning cylinders l 14 that are pivotally mounted on brackets 1 secured to the transverse beam 96. Operation of cylinders 114 will lift the punch-out cylinders 108 to an inoperative position, as shown in FIG. 7, completely outside of the rotating path of the pallets, and to a vertical position, as shown in FIG. 9, where the heads 112 are in position to enter the pallet openings 11 and press the casting from the pallet.

In order to prevent breakage of the concrete castings when they are free from the pallets, there are receiving arms 1 16 at the lowering station 22 which have an upper position wherein the casting seating surfaces 1 17 of the arms are just below the casting when in the pallet. The arms have a lower position in which the seating surfaces 117 are below the plane of a casting accumulating slide 118. A pair of the receiving arms 116 are shown, one being mounted beneath each end of the pallet position on a shaft 119 that has its ends journalled in bearings 120 fixed to an adjacent stanchion 90. Cylinders 121 are pivotally connected to brackets 122 secured to one of the I-beams 89, and have their piston rods 123 pivotally connected to the casting receiving arms. When the arms are in their upper positions, they will receive free castings and lower them onto the accumulating slide 1 18.

Slide 118 forms part of the tie, or other concrete casting, accumulating station 23. The slide consists of spaced rails 124 that are supported upon legs 125 so as to decline from a level just below the rotating heads 99 at the inverting station to just above ground level at the entrance end of the machine. The rails are formed of spaced channels 126 which support the actual slide rails 127. For most of the length of the slide, from the entrance end of the machine toward the inverting station, there are roller conveyors 128 mounted alongside and parallel to the slide rails 127. The tops of the rollers are slightly above the top of the slide rails, and castings moving down the slide will move freely by gravity along the roller section.

Castings lowered by the arms 116 onto the slide rails 127 are moved out of the inverting station area and down the slide by means of a pusher plate 129 actuated by a cylinder 130. Plate 129 is fixed to one end of a guide rod 131 journalled in a bearing 132 fixed to one of the channels 126. Cylinder is fixed to a beam 133 that extends between the channels of adjacent slides. Piston rod 134 of the cylinder is connected'to the guide rod 131 so that plate 129 will be moved longitudinally of the slide when the cylinder is actuated. There is one pusher plate assembly adjacent each of the slide rails.

After the casting is removed from the pallet, the rotating heads 99 are rotated to reverse the position of the pallet so that it is again right side up. The advancing rack 30 will then move forward and draw the now empty pallet from the inverting station and into the cable end removing station 20.

At the station 20 there is an end frame at each side of the main frame of the apparatus, consisting of spaced vertical posts 135 that are welded at their bottoms to the angle members 50 of the main frame 13. The posts are bridged at their top by a cross beam 136. Centrally of each beam 136 there is a bearing 137 in which trunnions 138 at the ends of a hammer mounting beam 139 are journalled. Beam 139 extends completely across the machine centrally of the cable end removing station. Near each end of beam 139 there is a bearing 140 for a shaft 141 on which the hammer 142 is freely swingable. The bearings 140 are so located that when the hammers hang vertically their driving plates 143 will be in contact with the inner faces of the headers of a pallet at the station. The hammers consist of spaced legs 144 pivotally mounted on shaft 141 and bridged by body plates 145, 146 and 147. The driving plate 143 also bridges the legs at their free ends. The hammer is moved to and from cable striking position by means of cylinders 148 which are pivotally mounted on short girders 159 depending from the cross beam 136. Piston rods 150 of the cylinders are connected to the body plate 145. 

1. An apparatus for removing cured pre-stressed concrete articles from pallets having means to hold cables stressed between the ends of the pallets and having openings in the bases of the pallets comprising, a pallet path, means to support the said path, means to move the pallets along the path to predetermined positions, means at one of said positions to cut said stressed cables at the pallet ends to free concrete articles from the pallets, means at another of said positions to engage and rotatably support pallets, means to rotate the pallets in said engaging and supporting means to invert the pallets, means overlying the pallet path and having downwardly projecting plungers to press freed concrete articles from the pallets, and means to cause relative vertical movement between inverted pallets to enter the openings in the pallet bases and press the articles from the pallets.
 2. An apparatus for removing cured prestressed concrete articles from pallets as claimed in claim 1 further comprising, means to receive and lower articles pressed from pallets.
 3. An apparatus for removing cured prestressed concrete articles from pallets as claimed in claim 1 further comprising, means to drive cut cable ends from the pallets.
 4. An apparatus for removing cured prestressed concrete articles from pallets having means to hold cables stressed between the ends of the pallets and having openings in the bases of the pallets comprising, a frame, a pallet path on the frame, means to move pallets along the path to predetermined positions, means on the frame located at one of the positions to cut tensioned cables at the pallet ends to free concrete articles from the pallets, heads rotatably mounted on the frame at another of said positions in face to face relation on opposite sides of the pallet path and having means to engage and support said pallets, means to rotate the heads to invert pallets supported between them, and means mounted on the frame overlying the pallet path between the heads and having downwardly projecting plungers to press freed concrete articles from pallets, and means to cause relative vertical movement between inverted pallets supported by the heads and the plungers to cause the plungers to enter the openings in the pallet bases and press the articles from the pallets.
 5. An apparatus for removing cured prestressed concrete articles from pallets as claimed in claim 4 wherein, the means having a downwardly projecting plunger is a fluid operated cylinder having a piston rod with a plunger head on the piston rod.
 6. An apparatus for removing cured prestressed concrete articles from pallets as claimed in claim 5 wherein, the fluid cylinder is pivotally mounted on the frame, and further comprising means to swing the cylinder to and from an operative position.
 7. An apparatus for removing cured prestressed concrete articles from pallets as claimed in claim 4 wherein, the means on the heads to support pallets includes a pair of spaced rails for engagement with the ends of pallets between the heads, and arcuate wear plates on opposite sides of the pallet path and beneath the pallet path forming retaining means to hold pallets in position on the head rails during rotative movement of the heads.
 8. An apparatus for removing cured prestressed concrete articles from pallets as claimed in claim 4 further comprising concrete article-receiving arms pivotally mounted on the frame below the pallet path between the heads to receive concrete articles pressed from pallets, and means to raise the arms to article-receiving position and to lOwer the arms to carry articles away from the pallet.
 9. An apparatus for removing cured prestressed concrete articles from pallets as claimed in claim 8 further comprising, a concrete article slide in the path of downward movement of the articles on the receiving arms, whereby articles lowered by the receiving arms are deposited on the slide.
 10. An apparatus for removing cured prestressed concrete articles from pallets as claimed in claim 9 further comprising, a pusher plate mounted on the frame at the end of the slide to start articles moving down the slide.
 11. An apparatus for removing cured prestressed concrete articles from pallets as claimed in claim 4 further comprising, means at still another of said predetermined positions to drive cut cable ends from the pallet headers.
 12. An apparatus for removing cured prestressed concrete articles from pallets as claimed in claim 11 wherein, the means to drive cut cable ends from the headers comprises a pair of hammers pivotally mounted on the frame for swinging movement downwardly and toward the inner sides of the ends of pallets on the pallet path beneath the hammers, and means to swing the hammers.
 13. An apparatus for removing cured prestressed concrete articles from pallets as claimed in claim 12 wherein, the frame comprises, a member rotatable on an axis transversely of the pallet path, and the hammers are pivotally mounted on the rotatable frame member. 